In diagnosis/medical treatment using an X-ray diagnostic apparatus, a patient is exposed to X-rays. There is available a technique of visualizing the distributions of X-ray incident doses and X-ray exposures to the patient. This technique allows a doctor to perform a surgical operation and X-ray imaging while monitoring an entrance skin dose to the patient. As a consequence, since the doctor can perform a surgical operation in consideration of X-ray exposure to the patient, it is possible to reduce the total incident dose and local incident doses to the patient. In the above technique, the apparatus grasps the position of the X-ray source, the position of the X-ray detector, and the position of the bed, but cannot recognize at which position on the bed a patient is placed. For this reason, it is necessary to estimate or measure the shape and position of the patient.
In the above technique, first of all, the patient is placed on the bed of the X-ray diagnostic apparatus. A model assumed to be most suitable for the patient is then manually selected from a database (or semi-automatically selected by referring to weight information and height information). Many specified models are registered in the database. That is, in the execution of the above technique, it is assumed that the model to be used in the above technique is selected from a plurality of specified models. In addition, the position of the selected model is manually aligned with the position of the X-ray diagnostic apparatus.
However, since the number of models is finite and mis-selection may occur, the difference in shape between the model and the patient directly leads to a measurement error in an entrance skin dose. In addition, if the actual irradiation range with respect to the patient is shifted from an exposure position on the model by a change in the body shape of the patient, difficulty in accurately grasping the position of the patient on the bed, the movement of the patient during an X-ray examination, and the like, an error occurs in the entrance skin dose.
Under the circumstances, when displaying and calculating an entrance skin dose in the above technique, it is expected to use a shape matching the actual shape of a patient and the position of the patient concerning the X-ray diagnostic apparatus instead of a model. For example, there is available a method of measuring the actual body shape of a patient and specifying the position of the patient concerning the X-ray diagnostic apparatus by using a video camera or installing various types of sensors on the bed.
When, however, using a video camera, a cover such as a drape covering an object sometimes inhibits the patient from being depicted in a video. In this case, it is not possible to grasp the accurate shape of the patient. In addition, even if an infrared camera is used as a video camera, it is only possible to grasp the accurate shape of the patient in one direction by using one camera.
In addition, using sensors imposes certain limitations on the detection of the shape of the patient. Even using, for example, a pressure sensor, a contact sensor, a capacitance sensor, and a temperature sensor as sensors will lead to the occurrence of a positional shift (difference) on a centimeter basis because of factors such as the lifting of part of the patient from the bed.